Cigarette filter to reduce smoke deliveries in later puffs

ABSTRACT

A smoking article having a tobacco rod adapted to produce mainstream smoke, and a filter having an upstream end portion and a downstream end portion, and wherein the filter is arranged to receive mainstream smoke at the upstream end portion. The filter includes a first filter segment of low particulate efficiency at the upstream end portion; a channeled flow segment adjacent to the first filter segment, the channeled flow segment including a flow channel establishing a substantial portion of a predetermined resistance to draw of the smoking article; a mouthpiece filter segment of low particulate efficiency at the downstream end portion; and a tubular body segment at least partially defining a portion of a cavity between the mouthpiece filter and the channeled flow segment. Tipping paper attaches the filter with the tobacco rod and includes an air-admissible ventilation zone at a location along the tubular body segment.

WORKING ENVIRONMENT

Heretofore, cigarettes with high levels of ventilation have usually hadunacceptably low levels of resistance to draw (RTD) unless some countermeasure was in place to make up for the shortfall in RTD. In the past,high-density cellulose acetate filter segments were used to address theshort fall. However such filtered segments tended to reduce tar delivery(FTC), with little or no effect upon gas phase components of mainstreamtobacco smoke, such as carbon monoxide (CO) and nitrogen oxide (NO).This solution tended to worsen the CO to tar (FTC) ratios in filtered(FTC tar) cigarettes.

Ventilation has a desirable attribute in that, when operating alone, itwill reduce both the particulate phase and the gas phase of mainstreamsmoke. However, highly ventilated cigarettes have drawbacks inresistance to draw (RTD) as previously discussed. It can be appreciatedthat with a flow restricting orifice in the cigarette filter, themainstream smoke is forced to flow through the orifice. With the filterventilation introduced downstream from this orifice, the ventilationlevel is dependent on the overall resistance to draw (RTD) upstream fromthe ventilation holes. For a given number of ventilation holes and size,the filter ventilation level increases as the upstream RTD increases. Ata given filter efficiency, increased filter ventilation reduces thesmoke tar delivery.

In a conventional filtered cigarette, per puff tar delivery increases assmoking progresses through the puff count. This is mainly due to thecombination of reduced filtration from the tobacco rod, re-vaporizationof tar build up on the tobacco rod from previous puff(s), and adecreased filter ventilation contribution as the puff (char line)progresses and the upstream RTD reduces. The tar delivery of the lastpuff could be twice as much as the first and/or second puffs. Reducingthe degree of change from early to later puffs in principle would permitfor a more consistent sensorial experience, and reducing the total tardelivery, without significantly affecting the overall smokingexperience.

Accordingly, it would be desirable for a smoking article to address thephenomena of inconsistent smoke deliveries from puff to puff, since itis known that the delivered tar from earlier puffs is less than thedelivery of the later puffs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a smoking article in accordance withone embodiment.

FIG. 2 is a cross-sectional view of the smoking article of FIG. 1 inaccordance with another embodiment.

FIG. 3 is a cross-sectional view of a smoking article in accordance withanother embodiment.

FIG. 4 is a cross-sectional view of the smoking article of FIG. 3, inaccordance with a further embodiment.

FIG. 5 is a graph showing the puff by puff total particulate matter(TPM) deliveries of a conventional cellulose acetate (CA) filteredcigarette.

DETAILED DESCRIPTION

In accordance with one embodiment, a channeled flow segment is designedsuch that during the process of smoking the cigarette, the resistance toflow of smoke through a channel within the segment increases as a resultof tar accumulation or build-up within the channel. The increasedresistance, as smoking progresses, causes the filter ventilation toincrease and the delivered tar is decreased in the later puffs. Inaccordance with another embodiment, the increased resistance to draw(RTD) and filter ventilation during the later puffs can also be designedso that it is difficult to smoke the last few puffs (where tar per puffcan be twice as much as the first few puffs) thereby reducing the totaltar delivery without significantly impacting the overall smokingexperience. In addition, depending on the size (inner diameter) and thelength of the flow channel, a desired pressure drop across the segmentcan be achieved.

Referring to FIG. 1, a preferred embodiment provides a smoking article10 comprising a tobacco rod 20 and a filter 30 connected with thetobacco rod 20 by an outer wrapper or tipping paper 28. Preferably, thefilter 30 comprises a first filter segment 40 at an upstream portion 32of the filter 30, a second or mouthpiece filter segment 50 at downstreamend portion 34 of the filter 30, and a channeled flow segment 60situated between the first and mouthpiece filter segments 40, 50. Inaccordance with a preferred embodiment, the first and mouthpiece filtersegments 40, 50 are low particulate efficiency filter segmentsconstructed from cellulose acetate tow.

As shown in FIG. 1, smoking articles 10 in the form of cigarettestypically include a generally cylindrical rod 20 of smokable material22, contained in a circumscribing porous wrapping material or paperwrapper 24. The rod 20 is typically referred to as a “tobacco rod” andhas a lit end or upstream end 12 and a downstream or filter end 14. Thesmokable material 22 is preferably a shredded tobacco or tobacco cutfiller. However, any suitable smokable material 22 can be used.

The filter 30 is adjacent to the filter end 14 of the tobacco rod 20such that the filter 30 and tobacco rod 20 are axially aligned in anend-to-end relationship, preferably abutting one another. The filter 30preferably has a generally cylindrical shape, and the diameter thereofis essentially equal to the diameter of the tobacco rod 20. The ends(i.e., upstream end 16 and downstream end 18 (i.e., mouth end or buccalend) of the filter 30 are open to permit the passage of air and smoketherethrough.

The filter 30 is preferably attached to the tobacco rod 20 by an outerwrapper or tipping paper 28, which circumscribes both the entire lengthof the filter 30 and an adjacent region of the tobacco rod 20. Thetipping paper 28 is typically a paper like product; however, anysuitable material can be used.

As shown in FIG. 1, the channeled flow segment 60 is adjacent to thefirst filter segment 50. In accordance with a preferred embodiment, thechanneled flow segment 60 including the flow channel 62 establishes asubstantial portion of a predetermined resistance to draw of the smokingarticle 10. The flow channel 62 is preferably coaxially orconcentrically positioned within the channeled flow segment 60. However,in an alternative embodiment, one or more flow channels 62 can bepositioned on an outer periphery of the channeled flow segment 60. Inaccordance with a preferred embodiment, the channeled flow segment 60and the flow channel 62 each have a length of about 1 mm to 15 mm. Theflow channel 62 also preferably has a diameter of approximately .5 mm to2 mm.

The channeled flow segment 60 may be constructed of paper, a plastic ora metal and more preferably made of a paper product or a biodegradableplastic or other suitable material having degradability properties. Inaccordance with a preferred embodiment, the flow channel 62 is generallystraight, having a relatively constant diameter such that the channel 62extends in a continuous direction without bending from an upstream endto a downstream end of the channeled flow segment 60. Alternatively, theflow channel can be a spiral channel, or other suitable configuration.

In accordance with an embodiment, the flow channel 62 is at least inpart defined by a cylindrical tubular member 48, which is constructedfrom a relatively heavy filter plug wrap or paper. The tubular member 48preferably extends from an upstream end to a downstream end of thesegment 60.

It can be appreciated that the channeled flow segment 60 is preferablysized to contribute sufficient pressure drop such that the smokingarticle 10 presents a resistance to draw of at least 50 mm water orgreater, and more preferably in the range of 70-120 mm water. It can beappreciated that as the channeled flow segments 60 becomes clogged, theresistance to draw and/or flow through the flow channel 62 increases dueto the tar build up. Preferably, the channeled flow segment 60 has adiameter of approximately 7.0 to 8.0 mm, and more preferablyapproximately 7.4 to 7.8 mm.

In accordance with one embodiment, a tubular body segment 64 at leastpartially defining a portion of a cavity 66 is situated between themouthpiece filter 50 and the flow channel 62 of the channeled flowsegment 60. The filter 30 can also include a second upstream tubularbody portion (not shown) that spaces the channeled flow segment 60 apredetermined distance apart from the first filter segment 40.

The smoking article 10 also preferably includes a ventilating zone 70comprised of a first row (and optionally second and possibly third rows)of ventilation holes or perforations 72, each of which extend throughthe tipping paper 28, the plug wrap 26 and the tubular body segment 64.

Preferably the ventilating zone 70 is located near or adjacent to thechanneled flow segment 60 so that air drawn through the ventilation zone70 is allowed to mix with the mainstream smoke from the flow channel 62before arriving at the mouthpiece filter segment 50. The distancebetween the ventilating zone 70 and the mouthpiece filter segment 50 ispreferably at least 5 mm and more preferably in the range of 5-12 mm. Inaccordance with a preferred embodiment, the holes or perforations 72 ofthe ventilating zone 70 achieve a ventilation level of the smokingarticle 10 of at least 25% and more preferably at least 50% to 90%.

During an initial puff or puffs, mainstream smoke is drawn from the litend through the tobacco rod 20 to the downstream end of the filter 30,and drawn through the flow channel 62. Thus, by the time of subsequentpuffs on the smoking article 10, the flow channel 62 is partiallyblocked. It can be appreciated that the resistance to draw (RTD) and theflow distribution of the flow channel 62 can be depend on severalfactors including the length of the filter 30 and the flow channel 62,the inner diameter of the flow channel 62, and the nature or type offilter materials within the first filter segment 40 and the mouthpiecesegment 50.

The first filter segment 40 and the mouthpiece filter segment 50 arepreferably a starch-based, polypropylene, or plasticized celluloseacetate tow, filter paper or other suitable material. The first filtersegment 40 and the mouthpiece segment 50 can also be constructed from agathered web (e.g., polypropylene web, polyester web, cellulosic web orstarch-based web).

In accordance with a preferred embodiment, as the smoking progresses,tar gradually builds up inside and at the ends of the flow channel 62.Resistance to flow through the flow channel 62 increases due to the tarbuild up as shown in FIG. 2, and as a consequence the filter ventilationincreases and the tar deliveries decreases in the later puffs. A moreconsistent puff-by-puff tar delivery is thus achieved attributable tothe lowered delivery of the later puffs. In addition, the increasedfilter ventilation results in a decreased amount of tobacco burnt andsmoke delivered.

In accordance with an embodiment, the increased resistance to draw (RTD)and filter ventilation during the later puffs can also be designed sothat it is difficult to smoke the last few puffs. It is generallyaccepted that the first few puffs or earlier puffs are more important interms of the smoking experience, and wherein the reduced tar deliveriesin the last few puffs from this novel filter design can have overall tarreduction with minimum impact on the smoking experience. It can also beappreciated that the flow channel 62 can be fine tuned to control thetar build up, by adjusting or changing the size of the channel 62,including the length and diameter thereof, so that theresistance-to-draw (RTD) is acceptable and ventilation of the filter 30achieves desired tar delivery from the smoking article 10.

In accordance with another embodiment, the flow channel 62 can includeor be coated with a material 49 (FIG. 2) such as a sintered porousplastic. In accordance with an embodiment, the flow channel is filledwith a sintered porous plastic. It can be appreciated that sinteredporous plastics can allow “dry” air flow at a given resistance to draw(RTD). Alternatively, at another given resistance to draw (RTD), due tothe capillary action of the sintered porous plastic materials, theresistance to draw (RTD) can increase when a “wet” stream is deliveredin the flow channel 62.

In accordance with another embodiment, as shown in FIGS. 3 and 4, theflow channel 60 can be in the form of a thin plate 100 (0.2 mm to 2 mmin thickness) with at least one orifice (or flow passage) 110 with adiameter of 0.2 mm to 0.6 mm. The number of orifices 110 is not limited,but preferably the plate 100 has 2-8 orifices, and is mostly determinedby the pressure drop introduced by this thin plate with orifices. Thepressure drop is preferably in the range of 100 to 500 mm water drop. Asthe smoking progresses, smoke tar gradually builds up and partiallyblocks the orifices 110 which cause pressure drop increase. Thispressure drop increase would force more air flowing through the filterventilation holes 72, or ventilation level increases. The increasedfilter ventilation will reduce air flowing into the burning coal andreduce the smoke generated. In other words, the cigarette filter 30 willhave lower ventilation in the earlier puffs and higher ventilation inlater puffs. The net effect of gradual increase of ventilation assmoking processes is more smoke in the earlier puffs and less smoke inthe latter puffs, resulting more consistent puff by puff smokedeliveries.

It is to be appreciated that in all embodiments, the filter 30 may beconstructed from simple combining techniques typically used in theindustry for manufacturing cigarettes at high speeds. Additionally eachembodiment includes support about the cavity 66 to provide desiredfirmness throughout length of the filter 30.

FIG. 5 shows puff by puff total particulate matter (TPM) (mg) deliveriesof a conventional cellulose acetate filtered cigarette. In general,smoke tar tracks with smoke total particulate matter (TPM). As shown inFIG. 5, the average total particulate matter (TPM) of the first threepuffs is 1.0 mg/puff, and the average of the last three puffs is 1.8mg/puff. The total particulate matter (TPM) from the whole cigarette is11.3 mg, with a total of 8 puffs. Accordingly, if the total particulatematter (TPM) from the last three or four puffs of the cigarette are keptat around 1.0 mg or so per puff, or similar to that of the first threepuffs, as indicated by the dotted line in FIG. 5, the smoking articles10 as shown in FIGS. 1-4 are able to deliver 8-9 mg total particulatematter (TPM) with a smoking experience similar to that of a 11 mg totalparticulate matter (TPM) product, at least for the first half ofsmoking.

It will be understood that the foregoing description is of the preferredembodiments, and is, therefore, merely representative of the article andmethods of manufacturing the same. It can be appreciated that manyvariations and modifications of the different embodiments in light ofthe above teachings will be readily apparent to those skilled in theart. Accordingly, the exemplary embodiments, as well as alternativeembodiments, may be made without departing from the spirit and scope ofthe articles and methods as set forth in the attached claims.

1. A smoking article comprising: a tobacco rod adapted to producemainstream smoke; a filter having an upstream end portion and adownstream end portion, the filter arranged to receive mainstream smokeat the upstream end portion, the filter comprising: a first filtersegment of low particulate efficiency at the upstream end portion; achanneled flow segment at a location downstream of the first filtersegment, the channeled flow segment including a flow channelestablishing a substantial portion of a predetermined resistance to drawof the smoking article; a mouthpiece filter segment of low particulateefficiency at the downstream end portion; and a tubular body segment atleast partially defining a portion of a cavity between the mouthpiecefilter and the flow channel of the channeled flow segment; and tippingpaper attaching the filter with the tobacco rod and including anair-admissible ventilation zone at a location along the tubular bodysegment.
 2. The smoking article of claim 1, wherein the channeled flowsegment is spaced from the mouthpiece filter segment by a distancesufficient to reduce impaction of a mainstream smoke component upon anupstream end portion of the mouthpiece filter.
 3. The smoking article ofclaim 1, wherein the air-admissible ventilation zone comprises a row ofperforations extending through the tipping paper and the tubular bodysegment.
 4. The smoking article of claim 1, wherein the ventilation zoneis spaced from the mouthpiece filter segment by a distance sufficient topromote mixing of air drawn through the ventilation zone and mainstreamsmoke drawn from the tobacco rod.
 5. The smoking article of claim 1,wherein at least one of the first filter segment and the mouthpiecefilter segments comprises cellulose acetate tow of low resistance todraw.
 6. The smoking article of claim 1, wherein the flow channel iscoaxially positioned within the channeled flow segment.
 7. The smokingarticle of claim 1, wherein the flow channel is in an outer periphery ofthe channeled flow segment.
 8. The smoking article of claim 1, whereinthe flow channel has a relatively constant diameter extending from anupstream end to a downstream end of the channeled flow segment.
 9. Thesmoking article of claim 1, wherein the flow channel is a spiralchannel.
 10. The smoking article of claim 1, wherein the flow channelincludes a sintered porous plastic.
 11. The smoking article of claim 1,wherein the channel flow segment is a a plate having at least oneorifice.
 12. The smoking article of claim 11, wherein the plate has athickness of less than 2 mm and the at least one orifice has a diameterof 0.2 mm to 0.6 mm.
 13. A filter having an upstream end portion and adownstream end portion and arranged to receive mainstream smoke at theupstream end portion, the filter comprising: a first filter segment oflow particulate efficiency at the upstream end portion; a channeled flowsegment at a location downstream of the first filter segment, thechanneled flow segment including a flow channel establishing asubstantial portion of a predetermined resistance to draw of the smokingarticle; a mouthpiece filter segment of low particulate efficiency atthe downstream end portion; and a tubular body segment at leastpartially defining a portion of a cavity between the mouthpiece filterand the flow channel of the channeled flow segment.
 14. The filter ofclaim 13, wherein the channeled flow segment is spaced from themouthpiece filter segment by a distance sufficient to reduce impactionof a mainstream smoke component upon an upstream end portion of themouthpiece filter.
 15. The filter of claim 13, wherein at least one ofthe first filter segment and the mouthpiece filter segments comprisescellulose acetate tow of low resistance to draw.
 16. The filter of claim13, wherein the flow channel is coaxially positioned within thechanneled flow segment.
 17. The filter of claim 13, wherein the flowchannel is in an outer periphery of the channeled flow segment.
 18. Thefilter of claim 13, wherein the flow channel has a relatively constantdiameter extending from an upstream end to a downstream end of thechanneled flow segment.
 19. The filter of claim 13, wherein the flowchannel is a spiral channel.
 20. The filter of claim 13, wherein theflow channel includes a sintered porous plastic.
 21. A method ofreducing total FTC tar delivery of a smoking article by drawingmainstream smoke during each puff through an upstream, channeled filtersegment and a downstream filter portion having a ventilation zone, saidupstream channeled filter segment accumulating tar as smoking progressesthrough a puff count such that delivered FTC tar is decreased in thelater puffs of the puff counts when compared to a conventionalcigarette.